1. The Field of the Invention
This invention relates to devices used to measure the bending motion of various regions of the human body. More particularly, the present invention is related to inclinometers which are used to measure the bending motion of regions of the human body.
2. The Prior Art
Range of motion measurements of various regions of the human body are important to determining the extent to which a patient's mobility has been impaired due to age, injury, or disease. Health care practitioners regularly measure the range of motion possessed by various regions of a person's body. Range of motion is generally measured in units of degrees. For example, if a person is able to rotate his head from shoulder to shoulder, referred to as cervical rotation, then the range of motion for that region of the body is about 90.degree. left and about 90.degree. right.
In the past, mechanical devices known as goniometers were manually manipulated by the medical practitioner in concert with the motion of the body region of interest and an approximation of the range of motion was determined by subtracting beginning and ending readings from a degree scale provided on the goniometer. In an effort to overcome the inaccuracies inherent in the use of goniometers, particularly when used by less experienced practitioners, gravity referenced devices were introduced. Such gravity referenced devices are generally referred to as inclinometers since they measure the motion of the body region with respect to the horizon, or more precisely, with reference to gravity. Such inclinometers consist of three general types: fluid filled devices which are accurate to about 7 degrees; weighted needle devices which are accurate to about 4 degrees; and, electronic devices which are accurate to about 1 degree and provide a digital display making them easy to use.
As the art progressed, even more accurate range of motion measurements were desired by practitioners. It was recognized that the motion of an adjacent body region influences the measurement of the range of motion of another body region of interest. For example, to measure the range of motion for cervical flexion and extension, i.e., bending of the neck forward and backward, any bending of the back will undesirably alter the inclinometer reading since the inclinometer is determining the movement of the neck with reference to gravity without regard to whether the movement of the neck region is due to the bending of the patient's neck or the bending of the patient's back.
In order to find the true range of motion for the patient's neck, the motion of the back must be subtracted from the motion of the patient's neck. Such differential measurements, for example, the difference between the motion of the neck region and the motion of the upper back region, provide the most useful and accurate range of motion determinations.
In order to automatically provide differential range of motion measurements, it has been proposed in the art to utilize two inclinometers connected to a desk top computer. Each of the inclinometers are individually attached to a particular body part, for example, the head and the upper back. Each of the inclinometers are also individually attached to the desk top computer via one or more respective cords. While such an arrangement provides differential range of motion measurements it also presents significant drawbacks.
The cables connecting the inclinometers to the desk top computer are cumbersome; they get in the way during the examination and restrict the distance which the practitioner can move the patient from the desk top computer. Also, the patient must be brought to the desk top computer and its attached inclinometers. The unnecessary movement of patients from one examination room to another examination room is confusing, disruptive, and interferes with the examination of other patients. The desk top computer is generally much more powerful, and thus more expensive, than needed for merely calculating differential range of motion measurements. The expense of the additional components which must be added to a desk top computer further increase the cost.
Another disadvantage is that the practitioner must look away from the patient in order to view the computer screen showing the operation and results of the device. Still further, a desk top computer utilizes line voltages of 100 volts or higher. Thus, medical device standards require that precautions be implemented to isolate the patient from any harmful electrical currents. The precautions taken to ensure electrical isolation of the patient add to the cost and complexity of a dual inclinometer scheme when a desk top computer is used.
In view of the drawbacks and disadvantages found in the current state of the art, it would be an advance in the art to provide a self contained differential inclinometer system which is portable and easy to use.